We investigated relation between micro-habitat heterogeneity and the benthic macro-invertebrates community at a concreate-lined urban stream, Ikejiri River that flows through Sanda City, Hyogo Prefecture, Japan. We sampled benthic macroinvertebrates with quantitative method and measured environmental factors such as vegetation cover ratio, depth, river-bed substrate subdividing the microhabitat into three types, that with vegetation cover, completely concrete cover and artificial small pool. Fifty taxa were recognized and the richness was the highest in the first type and the lowest in the third-type. The effects of the vegetation cover ratio for the number of taxa in each site by using Piecewise linear regression analysis showed that the richness was unexceptionally high more than 8% in the threshold value for the ratio against lower richness in less than 8%. We also performed the DCA (Detrended Correspondence Analysis) to make clear the ordination of the benthic assemblages. Ordination plot by site-score showed clearly different relative positions of three micro-habitat types. Correlation analysis between first axis of DCA and the environmental factors indicated positive relation with depth and negative with the vegetation cover ratio in the first axis. Ordination plot by speciesscore resulted the appearance of diagnostic indicator species to each habitat type. Our results revealed benthic community structure varied within partial instream habitat types, and suggested that small scale and local restoration such as by recovering vegetation cover and by setting up a small artificial pool might be effective tools even in a concreate-lined urban stream.
